Windows only: BitMeter is a small bandwidth-monitoring application packed with features to help you track and analyze your bandwidth usage.

If you're using an ISP that caps your bandwidth usage or you're just more curious than the average bear, you can keep an eye on things with BitMeter. On top of the basic features like a real time usage meter, BitMeter allows you to export your usage stats as a spreadsheet for further number crunching and remotely access your bandwidth data when away from your computer. Additionally, if you are in the unfortunate lot of having a restrictive data plan, you can set BitMeter to alert you when you've reached a user specified percentage of your bandwidth allotment. For another free Windows bandwidth meter, check out Net Worx. BitMeter is freeware, Windows only, and requires Microsoft .NET 1.1 or later. Thanks nfs!